Field of the Invention
The present invention relates to a power transmission apparatus for a vehicle. More particularly, the present invention relates to a power transmission apparatus for a vehicle having advantages of achieving multiple fixed speed stages by adding one planetary gear set and facilitating a generation and a torque assistance, and an electric vehicle mode driving by adding a motor/generator in a dual clutch transmission structure including two or three synchronizers, improving a fuel consumption and an acceleration performance.
Description of Related Art
An environmentally-friendly technology of a vehicle is a core technology which controls survival of a future automobile industry, and advanced vehicle makers have focused on the development of an environmentally-friendly vehicle to achieve environmental and fuel efficiency regulations.
An electric vehicle (EV) or a hybrid electric vehicle (HEV) that utilizes electrical energy, or a double clutch transmission (DCT) improving efficiency and convenience of a transmission may be examples of such a future vehicle technology.
Since the future vehicle has various technological restrictions such as a weight and cost, the vehicle makers have paid attention to the hybrid electric vehicle as an alternative of a realistic problem for meeting exhaust gas regulations and improving fuel efficiency performance and have entered into keen competition for commercializing the hybrid electric vehicle.
The hybrid electric vehicle is a vehicle using two or more power sources. Two or more power sources may be combined by various schemes and a gasoline engine or a diesel engine using the existing fossil fuel and a motor/generator driven by electrical energy are mixed and used as the power sources.
The hybrid electric vehicle generally utilizes an engine and a motor/generator, and utilizes as a primary power source a motor/generator having a relatively excellent low-speed torque characteristic at a low speed and utilizes as the primary power source an engine having a relatively excellent high-speed torque characteristic at a high speed.
As a result, the hybrid electric vehicle is excellent in fuel efficiency enhancement and reduction of exhaust gas because an operation of the engine using fossil fuel stops and the motor/generator is used at a low-speed section.
A dual clutch transmission (DCT) may be an example of a transmission applicable to such a hybrid electric vehicle, and the DCT may include two clutches applied to a manual transmission scheme, and thereby enhances efficiency and convenience.
The DCT alternatingly activates odd-numbered stages and even-numbered stages by alternatingly operating two clutches, and thereby improves continuity in torque transmission.
However, the DCT shows relatively high degree of clutch wear and energy loss in starting of a vehicle and rearward slip in starting of a vehicle on a slant. Furthermore, the DCT is typically controlled with a short shift-control period considering low heat capacity, and thus may easily show a shift shock.
Furthermore, to apply the DCT to a hybrid electric vehicle, an appropriate arrangement of a motor/generator as a power source may be devised.
The information included in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and may not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.